1. Field of the Invention
The present invention relates to an information processing apparatus and an information processing method, and more particularly, to an information processing apparatus and an information processing method, capable of achieving a great reduction in a delay caused by a decoding process and an inverse wavelet transform process.
2. Description of the Related Art
A JPEG (Joint Photographic Experts Group) format and a JPEG2000 format are widely used image compression algorithms according to standards established by the ISO (International Standards Organization). In general, when a discrete cosine transform (DCT) is used in an algorithm and a relative large number of bits are assigned, the algorithm can provide good encoded images and good decoded images.
In recent years, research efforts have been made on methods of encoding an image using a filter bank, which is a combination of a high-pass filter and a low-pass filter, in such a manner that given image data is divided into a plurality of frequency bands and encoding is performed separately for each band. Among these methods, much attention has been given to a wavelet transform encoding method, because of its advantage that unlike the DCT method, no block distortion occurs. Thus, the wavelet transform encoding method is expected to replace the DCT method.
In JPEG2000 established as an international standard in January 2001, a combination of the wavelet transform and a high-efficient encoding algorithm (bit modeling in units of bit plane and arithmetic encoding) is used to achieve a great improvement in encoding efficiency compared with the JPEG method.
The wavelet transform basically includes a process of filtering given image data in both horizontal and vertical directions thereby hierarchically separating low-frequency components from other components (see, for example, Japanese Unexamined Patent Application Publication No. 10-283342).
The coefficient data (frequency components) obtained as a result of the wavelet transform process on the image data is transformed into original image data via an inverse wavelet transform process. In the inverse wavelet transform process, the image is reconstructed by performing a synthesis filtering process on the high-frequency components and low-frequency components over all division levels from the highest level to the lowest level.
Encoding systems using the wavelet transform and the inverse wavelet transform are usable in video conference systems, video game systems, or other various systems in which image data is transmitted. In such a system, at a transmitting end, image data is wavelet-transformed, and coefficient data obtained as a result of the wavelet transform is encoded. The resultant encoded data is transmitted to a receiving end. At the receiving end, the received encoded data is decoded into coefficient data, and the obtained coefficient data is inverse-wavelet-transformed into original image data. In general, the encoding/decoding is performed according to the procedure described above.